Evaporator plates



Sept. 15, 1959 5LASS CLOTH 22 P. C. MILLER, JR

EVAPORATOR PLATES Filed July 22, 1957 22* GLASS CLOTH 2| GLASS WOOL 20 ALUMINUM SCREEN Zl- GLASS WOOL INVENTOR.

PAUL c. MILLER, JR.

BY 6mm 5 mm ATTORNEYS United States Pate 2,904,258 'EVAPOR'ATORPLATES Paul C. Miller, In, Detroit, Mich, assignor' to 'Fibe'rcraft Products, Inc, Detroit, Mich.

Application July 22, 1957, Serial No. 673,221 '5 Claims. Cl.'Z39-53) This application relates to evaporator plates and particularly'to T slaaped evaporator plates such as are-used in hot air'furnace humidifiers or 'the like for thepuI- poses I of becoming saturated "with water in pans of the humidifiers and evaporating such water by contact of thewet-tediplateswith a moving stream ofhot furnace air.

Evaporator platesfor this purpose are 'old and wellkno'wnand it -has been propose'dto make such plates of awariety'of 'materials such as ceramic, felt, fusedglass -wool,'etc.

In this application, I disclose a novel evaporator plate 'composed of unfused glass 'fibers I and aluminum screening, and I alsodisclose a novel processfor fabricating 'suchplate.

For an understanding of the plate"hereof, and of the process for I making it disclosed herein, reference should 'be 'had to the followingspecification which relates to the appended drawing.

' In thisdrawing, the 'singlefigure is arnenlarged scale perspective view'of an evaporator plate of the invention.

Referring to thedrawings, it will'be observed thatthe evaporator plate hereofincludes the following parts: 20, 'a's'creenof aluminum mesh; 21,1two blankets of fibrous glass wool felted batting compressed from their original flufliness to be a relatively thin'blanket; "22, .two outer -'-faeings "of wovenglassfiber cloth considerably thinner than the'blankets; and '23, stitching of glass fiber thread.

The screen.'Ihe screen 20 is-of aluminum mesh suchas ily screening known to the trade as 18-14 mesh-and of wire which may be in a preferred embodiment of 0.0018 inch thickness. Being of aluminum mesh, it will not corrod'e as' quickly as ferrous metal screening when used in water pans of furnace humidifiers and likewisehas a 'high'enough'melting point so as not to melt under the impactfof'hotffiirnace air.

Othenmaterialshave'been considered by me but have "been found'wan-ting. "For example, copper screening has too lo'w a melting point and this is equally'true of plastic mesh or screening. Ferrous metal screening such as iron orste'el would corrode. Non-corrosive steel mesh sueh'a's stainlesesteelis considerably more expensive than 'aiunnnumi "Fiber glass screeningwou-ldbe satisfactory *excepvthattherpresently available fiberrglass mesh con- =tains ahinding resin for bonding the-mesh warp'and woof threads an'd such binding resin would melt away in a furnace and the screen mesh made of fiber glass would "separate intoloose threads. 7

The aluminum mesh functions to rigidity the iplateand also-functions to prevent shreddingoff of the edges of the plate. It also functions to interlock the stitching for increased effectiveness of such' stitching.

In addition, theal-uminummesh furnishes a'high degree ofzprotection to the steeltrays or 'water pans employed in conventional humidifiers. These arepainted but not always is the paint secure and consequently'such :steel 'trayshave'expose'd areas which have a tendency to rust and corrode'in use. When-the steel isexposed due to a break-in the painting, and in aluminum mesh evaporatorplate such as I have-here disclosed is employed as the evaporator plate,-the aluminum mesh sets up a galvanic action whereby the steel pan does not corrode, but the aluminum mesh, and thus the evaporatorplate as a whole corrodes and becomes self sacrificing becausethe aluminum mesh, rather than the steel tray would be corroded by such galvanica'ction. The aluminummesh evaporator plate hereof is expendable because it is the preferred and accepted custom to replace evaporator plates yearly.

The blankets.-The blankets-2'1 are initially very-thick the assembly being about one inch thick soft'fiufiy blanketsof fiber glass batting. At the outset, it is treated as the water saturated portions of the plate and which function for evaporation. V

The facings.The facings 22 are of thin cloth woven of glass f'fibers or strands of threads and normally untreated. However, it is to be understood that in the normal processing andmanufacture of glassclothfrom glass threads a certain quantity of organic oil accumulates on the cloth during the weaving and the process of forming the plate hereof incorporates the decomposing and destruction of such oil so that the facings'are'left free of 'such oil when the plate is completed. The fa'cings are extremely thin and considerably assist in the evaporator function of the plate whereby a plate made of blankets and'facin'gs With an'alurninum mesh central screen is far more efiective for evaporation than a plate made only of glass wool blankets. In addition, the facings are relatively smooth and thus do not shred in use andship- 'ment and also have a considerably lesser tendency to become coated with dirt and bacteria in use "and in handling than would be the case with'platesmade with blankets alone, and thus are far more satisfactory not only from the point of View of appearance and handling and customer'impact, but also from the point of view of evaporation inasmuch as there is no dirt to clog up the evaporator pores of the plate.

While the facings are of extremely fine meshwoven cloth it is to be observed that they are rough in the sense that they furnish an extremely large area for evaporation, considerably larger than-Would be the case with blankets of glass 'wool alone.

The stitching.-Threads-23 of glass fiber-are used as stitching and these threads interlock with the aluminum -mesh screen 20 to give an improved mechanical securing of the parts together in an unlaminated plate.- Because saturation with a plasticizer of resin such as the phenol formaldehyde previously mentioned.

Thegplate'formed of these plies is then subjected to heat and pressure suflicient to thermoset the resin and cause the plies to adhere and thus form a laminated plate. A pressure of 75 pounds per square foot applied for 90 seconds at 450 F. has been found satisfactory. The result of this step is to produce a semi-rigid board.

The blankets are initially about one inch thick and. are reduced during the first heating step to a thickness of approximately 1 of an inch, or a reduction of 16 to one.

Such a board, of considerable area, and quite rigid, is then slitted into five inch strips, that width being the height of the evaporator plate from its lower edge to its upper edge.

Thereupon the five inch quite rigid strips are stitched along the stitch lines shown using glass threads 23 for such stitching and with the stitches passing through and interlocking to the aluminum mesh 20. The lines of stitching are parallel to the upper and lower edges of the five inch strips which form the upper and lower edges of the evaporator plate.

The threads used for stitching are of a specification as follows; 10,350 feet of thread per pound of Weight with a tensile strength of 14.3 pounds per thread.

These five inch stitched rigid laminated strips are then baked in a baking oven sufficient to decompose the resin and evaporate it, and delaminate the plate, and likewise, suflicient to destroy organic components of the blankets and facings and also to decompose and destroy any oil that may have been accumulated on the facings during the weaving of the glass cloth. The result is to leave the blankets and the facings of glass only, without organic components. It has been found that a baking for four and a half hours at a temperature of 810 F. without pressure in a closed atmosphere is satisfactory for this purpose.

Thereupon, the five inch strips are die-cut to the shape shown to form T-shaped evaporator plates.

While, in the final baking step, it has been found that four and a half hours at 810 F. is one example, other examples are as follows; a range of 700 to 900 F. at a time ranging from 10 hours down to three hours.

These temperatures are determined as follows: 900 F. is maximum; otherwise at higher temperatures the aluminum mesh 20 begins to soften; 700 F. is minimum; otherwise an excessive time is required for the baking step. Experience has demonstrated that four and a half hours at 810 F., in a range of ten to three hours at 700 to 900 F. is most satisfactory.

During the stitching and die cutting steps, the stitching and die cutting operations tend to smoothen out any puckering that is caused, as is often the case, by the expansion of the aluminum mesh 20 more than the glass blankets and facings during the heating in the thermosetting and laminating step, and in the baking or delaminating step.

The temperature in the laminating step as well as in the final baking or delaminating step, should be low enough to minimize the puckering due to the greater expansion of the aluminum than of the glass so that the puckering is so little that it can be absorbed by the smoothening that takes place during the stitching and the die cutting steps. Thus, experience has demonstrated that while the stitching step and die cutting step will eliminate some or most and possibly all of the puckering that takes place during the prior heating steps of laminating and baking, experience will determine how much heating can be applied in these heating steps without heating excessively to cause excessive puckering, in an amount that cannot be eliminated by the smoothening that takes place in the stitching and die cutting steps which follow the heating steps.

Advantages.-While many of the advantages have previously been set forth, some of them will hereafter be described even at the risk of repetition.

An evaporator plate formed as described wets completely almost immediately upon immersion and tests have shown a complete wetting within 20 seconds after the dipping of the lower end of the evaporator plate into a water pan. This contrasts favorably with evaporator plates now known which require a considerably longer time for complete wetting.

Another way of stating the foregoing is to state that the evaporator plate here shown has a considerably higher degree of capillarity than is true of certain plates such as are now being used.

Still another advantage is the relatively low cost of evaporator plates made according to the foregoing descniption, the costs being considerably less than evaporator plates now known, considering the factors of quality and effectiveness.

The evaporator plates hereof are considerably lighter in weight than ceramic plates and thus cost considerably less for shipment.

The evaporator plates hereof are non-frangible and non-brittle and thus may be easily handled without breakage and this is an important factor in the shipment and replacement of evaporator plates.

The evaporator plate hereof, however, is rigid enough so as to be self-supporting in use. When the lower edges are rested on the upper edges of water pans, the evaporator plates hereof are rigid enough to maintain them selves free standing and not become limp in use to bend over.

The evaporator plates hereof are non-organic and consequently there is no possibility of bacteria action and rotting, as would be the case with typical felted wool materials such as have been proposed.

While the evaporator plates hereof are smooth to the touch, and have a low degree of surface adhesion to floating dirt particles in the water pan and also to dirt and other particles in the hot furnace air, they are nevertheless rough surfaced sufiiciently to give an exceptional high quality evaporating surface which gives a high degree of evaporation effectiveness for these plates.

The glass wool blankets of the evaporator plates hereof, being faced with cloth, will not shred or abrade in handling, shipment or use.

An exceptionally high quality mechanical interlock is provided between the glass threads of the stitching and the aluminum mesh screen 20 and this gives an exceptionally fine mechanical effect which holds the plies of the plates together, even over a long period of handling, shipment, and use in hot air furnaces. The threads are stitched through the screen and the screen is thus interlocked to the facings.

The evaporator plate hereof Will not only be free of shredding on the faces due to the facings employed, but likewise will be free of shredding along the edges where the facings are not effective and this is assured by the presence of the aluminum screen 20 in the center of the plate.

The evaporator plate hereof has been found to function so satisfactorily for wetting that even under extreme conditions of evaporation, the plate will remain constantly wet, their ability to pick up water from the pan being considerably greater than the effect of hot furnace air from the typical furnace under typical forced air heating to remove water from the plates.

An evaporator plate presents a special problem in evaporation because of its T-shape which provides an inlet for water into the plate about /2 the area of the upper part as against the lower part with the upper part being the part that provides the greatest degree of evaporation. The T-shape of the evaporator plate is a shape that has been accepted by the art and is today standard in that art and that T-shape sets up a special problem of evaporation as against water feed to the plate because the evaporator area is about twice the water feed area and the plat? hereof has been found to be an exceptionally fine solution to that special problem created by the T'-shape demanded by the art.

As contrasted with ceramic plates, the evaporator plate hereof cannot become clogged by mineral deposits from the water because the glass fiber plate hereof has a considerably greater proportion of cells and pores than the ceramic plates of the art and hence the evaporator plate hereof will not clog so quickly and under normal conditions of use will function satisfactorily over several heating seasons.

It will be observed that the evaporator plate hereof is fibrous glass rather than fused glass and despite the two heating steps, laminating and final baking, the glass fibers remain in fibrous condition and at no time are fused to one another. The heating steps hereof are at sufficiently low temperatures and times so that the glass fibers do not fuse. Even the final baking step functions merely to decompose the organic components and release them in volatile form and delaminate the plate, and all this without fusing the glass fibers.

Fiber glass is far superior to felt for evaporator plates not only because of its greater resistance to bacteria and fungus action but also because of the impossibility of the fiber glass burning in a furnace. Cotton and wool felts and paper felts that have been proposed are not only subjected to bacterial and fungus action when used in furnaces, but also can burn and often do burn with possible danger and certainly with a complete destruction of the plate and its evaporator function.

While the plate hereof has been shown in planar form die cut from a sheet, it can if desired be formed by molding into curved and flexible shapes and irregular contours as desired, characteristics which are not found in evaporator plates that have been proposed to be made of fused glass or ceramic.

When the laminated board of large area is cut into five inch strips, the cutting lines are arranged on a 45 angle to the Warp and woof of the facings to avoid shredding of these facings with the result that the stitch lines and edges of the die cut evaporator plate will be on 45 angles to the warp and woof of the facings in the finished product.

Now having described the evaporator plate hereof and its method of manufacture, reference should be had to the claims which follow.

I claim:

1. Flexibly deformable evaporator plate laminate having sufficient rigidity to retain its plate form comprising a fine mesh stiffening aluminum screen, a layer of compacted matted fiber glass upon both faces of said screen and an outer layer of woven fiber glass cloth on each outer surface of the compacted fiber glass layers, the laminate being secured into a compact integral body by stitches of glass fiber thread.

2. An evaporator plate comprising a laminate as defined in claim 1, said laminate being formed to T-shaped evaporator plate units.

3. Flexibly deformable evaporator plate laminate having sufiicient rigidity to retain its plate form comprising a fine mesh stiffening metallic screen, layers of compacted and matted fiber glass upon both faces of said screen and free of fused fiber glass particles, oily and resinous coatings and bonding substances whereby the fibers are readily separable and an outer layer of woven fiber glass cloth on each outer surface of the compacted fiber glass, the compacted laminate being secured to a compact integral body by stitches of glass fiber threads extending from surface to surface.

4. An evaporator plate comprising the laminate defined in claim 3 reinforced by a central fine mesh aluminum screen, and cut to a T-shaped evaporator plate unit.

5. Flexibly deformable evaporator plate comprising multiple layers secured into a compact flexible laminated body having sufficient rigidity to retain its plate form, the said laminate comprising a porous flexible stiffening layer, a layer of compacted matted glass fiber upon both faces of said porous stiffening layer, an outer layer of woven fiber glass cloth on each outer surface of the compacted fiber glass layers, said laminate being secured into a compact integral body by stitches of inorganic fiber thread resistant to destruction at temperatures of the order of 700 to 900 F.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,711 Rosenowe June 5, 1934 2,184,316 Plummer Dec. 26, 1939 2,263,217 Lillie et a1 Nov. 18, 1941 2,271,829 Powers Feb. 3, 1942 2,391,558 Essick Dec. 25, 1945 

5. FLEXIBLY DEFORMABLE EVAPORATOR PLATE COMPRISING MULTIPLE LAYERS SECURED INTO A COMPACT FLEXIBLE LAMINATED BODY HAVING SUFFICIENT RIGIDITY TO RETAIN ITS PLATE FORM, THE SAID LAMINATE COMPRISING A POROUS FLEXIBLE STIFFENING LAYER, A LAYER OF COMPACTED MATTED GLASS FIBER UPON BOTH FACES OF SAID POROUS STIFFENING LAYER, AN OUTER LAYER OF WOVEN FIBER GLASS CLOTH ON EACH OUTER SURFACE OF THE COMPACTED FIBER GLASS LAYERS, SAID LAMINATE BEING SECURED INTO A COMPACT INTEGRAL BODY BY STITCHES OF INORGANIC FIBER THREAD RESISTANT TO DESTRUCTION AT TEMPERATURES OF THE ORDER OF 700* TO 900*F. 